The present invention relates to heat exchangers.
More particularly, the present invention relates to a heat exchanger which is suitable for use in the heating system of a motor vehicle and which has a housing through which flows a first medium which is to be heated up, the housing having a plurality of parallel conduits for a second medium which is to be cooled down, this second medium being constituted, for example, by the exhaust gases of an internal combustion engine, normally the engine of the vehicle in which the heating system is installed.
One example of such a heat exchanger is shown in German Pat. No. 532,606, in which there are a plurality of parallel conduits or tubes which are arranged within a cylindrical housing. The exhaust gas of the internal combustion engine is made to flow through all of these conduits in the same direction, and the remainder of the housing is traversed by the fluid medium which is to be heated up.
A heat exchanger of the above type has the advantage that the conduits for the medium to be cooled down are properly positioned so as to be subjected to the first medium, i.e., the medium which is to be heated up and which itself is therefore at low temperature. Splitting up the flow path for the second medium, i.e., the medium which is to be cooled down--this, in the case of an installation where this medium is used in the heating system of a motor vehicle, will be the exhaust gas coming from the engine--by providing a plurality of conduits, results in a large surface being exposed to the first medium, while providing an overall compact construction requiring little space. The more conduits for the second medium, the greater the efficiency of the heat exchanger. But even if the heat exchanger is provided with a large number of conduits for the second medium, the second medium will still be relatively hot when it exits the heat exchanger. If, then it becomes impractical to add still further conduits, the only way to increase the efficiency of the heat exchanger to the point where the temperature of the second medium exiting the heat exchanger will remain within practical limits, would be to lengthen the heat exchanger. However, there are limits beyond which the heat exchanger cannot be lengthened, lest it become so long that it would no longer be practical to use it as part of the heating system of a motor vehicle. In other words, the overall length of the heat exchanger can, in practice, not exceed a certain maximum, and it has been found that so long as the number of conduits for the second medium as well as the length of the heat exchanger must be kept within certain limits, the exhaust gases leaving the heat exchanger will still be excessively hot.
It is, therefore, the primary object of the present invention to provide a heat exchanger of the type which overcomes the mentioned drawbacks, namely, to provide a heat exchanger which, without significantly increasing the overall dimensions as compared to conventional heat exchangers, affords a greater heat transfer between the two media, and thus operates at higher efficiency than heretofore known heat exchangers of this type.
It is another object of the present invention to provide an improved heat exchanger of the above type in which condensate formed in the heat exchanger is removed so as to avoid the condensate from building up within the heat exchanger and so as to prevent the condensate from damaging any equipment connected to the outlet of the exchanger.